1. Field of the Disclosure
The disclosure relates generally to a light-emitting diode and a method for operating the same, and more particularly to a light-emitting diode module and a method for operating the same.
2. Description of Prior Art
AC-driven LED lighting technology, also called AC LED lighting technology, prevails in recent years. Besides compatibility with conventional lighting apparatuses, the heat-dissipation problem produced in the DC LED lighting technology can be significantly reduced, thus saving energy, reducing carbon emissions, and increasing whole luminous areas.
The circuit for driving the AC LEDs has two categories: one is an inverse-parallel topology (as shown in FIG. 1A) and the other is a bridge-rectifying topology (as shown in FIG. 1B). For the inverse-parallel topology, the LEDs are bi-directional micro-diode structures. The LED micro diodes are etched on a substrate and then split and insulated. Afterward, each two micro diodes are inversely connected in parallel by a metal bridge and then the inverse-parallel micro diodes are connected in series to form N-set AC driven light-emitting diodes. Hence, the amount of the required micro diodes is 2×N. However, only half of the micro diodes simultaneously illuminate when all of the micro diodes are driven by the AC driven voltage. Accordingly, the main disadvantage of the inverse-parallel AC driven LEDs is that instantaneous luminous areas and availability are not high.
For the bridge-rectifying topology, the micro diodes are connected in a bridge structure. Also, an appropriate amount of the LEDs is driven by the AC voltage according to the required voltage, current, and input power. Although the bridge-rectifying topology can increase instantaneous luminous areas, the availability of the micro diodes is not ideal. That is because the micro diodes on a common bridge leg can illuminate during both the positive-half cycle and the negative-half cycle but the micro diodes on other four bridge legs only illuminate during the corresponding half cycle.
Reference is made to FIG. 2A which is a circuit diagram of a prior art AC driven light-emitting diodes having a bridge rectifier and FIG. 2B is a schematic waveform outputted from a circuit structure in FIG. 2A. As shown in FIG. 2A, the micro light-emitting diodes are supplied through an external AC voltage source Vac. The external AC voltage source Vac is rectified into a DC voltage source (not labeled) by a bridge rectifying unit (not labeled). The micro light-emitting diodes are driven by the DC voltage source and controlled through a constant-current scheme. The micro light-emitting diodes can be lightened when a magnitude of the driven voltage is greater than that of a total forward voltage of the light-emitting diodes because the light-emitting diodes are electrically connected in series. As shown in FIG. 2B, the driven voltage increases with the increasing external AC voltage source Vac when the driven voltage is greater than the total forward voltage, namely a turned-on angle θon is met. In this condition, the light-emitting diodes continually illuminate and a constant-current Ic flows through the light-emitting diodes. On the other hand, the light-emitting diodes are off when the driven voltage is less than the total forward voltage. In a half cycle, a lighting time interval θe is a period that the light-emitting diodes are illuminated, which is shown between the turned-on angle θon and the turned-off angle θoff. Accordingly, the main disadvantage of the bridge-rectifying AC driven LEDs is that luminous efficiency is too low.
Accordingly, it is desirable to provide a light-emitting diode module and a method for operating the same. A piecewise current control (including a piecewise constant-current control and a piecewise variant-current control) is provided to improve luminous efficiency and increase availability of the light-emitting diodes. In addition, a system in package (SIP) topology is provided to simplify the package process and minify the light-emitting diodes.